1. Field of the Invention
This invention relates to a zipper component tape or strip for resealable plastic bags and the like and a method for forming the zipper component. More particularly, this invention relates to a zipper component wherein a continuous molten stream of thermoplastic material is formed as a base and brought into contact with a continuous carrier web driven by a series of rollers. Mating profiles are extruded onto the base, and the extrudate is stripped from the carrier web before the extrudate makes a complete circuit around the web.
2. Description of the Prior Art
In known processes for forming extruded zipper profiles for resealable plastic bags such as that described in U.S. Pat. No. 4,741,789, a base member is extruded and deposited onto a bag film web. A profile member is thereafter extruded and deposited onto the base member, thus adhering the profile to the bag film web. Because the profile and base members are deposited directly onto the bag film web immediately after extrusion, the bag film web must be of such a material and configuration as to be subjected to the disclosed process. Thus, the effectiveness of such processes is limited.
U.S. Pat. No. 4,894,975 discloses a method of manufacturing reclosable plastic bags in a vertical form and seal machine wherein a strip or tape carrying the profiles is used to provide the closure for the bag and to complete the bag formation.
U.S. Pat. No. 5,188,461 describes a method of manufacturing profile portions for packings, wherein the profiled portion is not deposited directly onto the packing. According to the method disclosed, a profiled outer layer is secured to an intermediate binding layer, which is secured to a base layer. The base layer is preferably made of the same material as the packing, allowing the base layer to be secured to the packing. By requiring the foregoing three layers, the disclosed method is not cost effective.
Other known methods of forming zipper components have used the extruded profile to pull itself through the equipment for manufacturing the same. To minimize deformation of the extruded profile due to tensile forces created in such methods, it is necessary to cool and solidify the extrudate as quickly as possible after extrusion. Water baths and cooled air have been utilized to cool and solidify the extrudate. However, such quenching methods do not permit typical post-extrusion forming of the extrudate. Further, such quenching methods do not eliminate deformation of relatively small unsupported profiles by tensile forces caused by the manufacturing equipment.
Therefore, in order to alleviate these problems, it is an object of the present invention to provide a zipper component and a method for forming a zipper component which does not expose the extruded profile to potentially damaging forces. Another object of the present invention is to provide a zipper component and a method for forming a zipper component wherein a support for the extruded profile does not become part of the finished zipper component. Yet another object of the present invention is to provide a low-cost method for forming a zipper component.